MS440 spark plug question

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wseibert

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I just realized that the MS440 that I recently got had a Champion CJ8 spark plug, but the manual specifies a Champion RCJ 6 Y. Like a bozo I went and replaced the CJ8 with the same one without checking the manual.

Will a CJ8 work in my saw? More importantly, what effect did running a CJ8 have on my saw? When I pulled it out, it had white stuff coating the end. I'm wondering because when I got it my saw had a burnt up chain, bar and clutch. I'm wondering if the wrong spark plug could have caused that. I have not run the saw myself except for a bit of testing. Hasn't seen wood yet.

Clearly the saw was run hard, possibly with a dull chain, for a long time. I'm still wondering why there was white stuff on the plug (which I think means lean mixture).

Any thoughts appreciated. Thanks!

Will
 
wseibert said:
I just realized that the MS440 that I recently got had a Champion CJ8 spark plug, but the manual specifies a Champion RCJ 6 Y. Like a bozo I went and replaced the CJ8 with the same one without checking the manual.

Will a CJ8 work in my saw? More importantly, what effect did running a CJ8 have on my saw? When I pulled it out, it had white stuff coating the end. I'm wondering because when I got it my saw had a burnt up chain, bar and clutch. I'm wondering if the wrong spark plug could have caused that. I have not run the saw myself except for a bit of testing. Hasn't seen wood yet.

Clearly the saw was run hard, possibly with a dull chain, for a long time. I'm still wondering why there was white stuff on the plug (which I think means lean mixture).

Any thoughts appreciated. Thanks!

Will
Click to expand...
A burned up bar and chain is mostly caused by running dull chains and not enough oil getting to the chain. A improper tuned carb is what causes lean condition not a sparkplug. It is best to run the proper specified sparkplug but a CJ8 would not hurt the engine, I have run Champion plugs since the late 50`s and even though some have reported the plugs as being problematic I have not seen that issue myself. I mostly use NGK plugs these days because they more easy for me to acquire, I buy them by the box.
 
pioneerguy600 said:
A burned up bar and chain is mostly caused by running dull chains and not enough oil getting to the chain. A improper tuned carb is what causes lean condition not a sparkplug. It is best to run the proper specified sparkplug but a CJ8 would not hurt the engine, I have run Champion plugs since the late 50`s and even though some have reported the plugs as being problematic I have not seen that issue myself. I mostly use NGK plugs these days because they more easy for me to acquire, I buy them by the box.
Click to expand...

I try to find boxes that were made in Japan.
 
I liked Champion plugs and had no issues with them , they were common at all supply outlets here until the Japanese engines like Honda and Kubota became widely distributed as in generators, gas water pumps and auxillary engines/ woodsplitters etc. That is when NGK plugs became more readily available, more so than Champs
 
ballisticdoughnut said:
At work we use WSR6F Bosch or NGK BPMR7A. Either one will work just fine but I prefer the NGK.
Click to expand...
I bought the Champion CJ8 at an auto parts store and it cost $3. When I went to exchange it for the right one, they didn't have the Champion and sold me the NGK for $0.79 more. Glad I didn't go to a Stihl dealer!

As for the spark plug chart posted by Woodslasher, the CJ8 plug that was in my saw when I bought it looked most like the first one labeled 'hot and lean', having a whiteish residue on it. Though I don't see much difference between that one and the one above and to the right labeled 'good'.

Thank you for all the replies. I'm learning that the whitish residue on the spark plug is related to fuel mix only, and not to the fact that the chain, bar and clutch drum were burnt up thorough lack of bar oil, overuse with a dull chain, or both.

Will
 
pioneerguy600 said:
I get them through our local automotive supplier these days as a local Stihl dealer wanted $25. for one plug last time I went there for anything. Where they are made , never noticed.
Click to expand...

NGKs were made in Japan , but some are from Brazil now, and possibly China too. I try not buy anything Chi-Com.

I still have some German Bosch from when I bought some boxes years back, I believe they too have started to employ the Communists.

1 bosch 3.jpg

I ran Autolites for quite a while in my N tractor. For a while they went to China and they were horrible. Started to rust a week after they were put in. They might have started making them in Mexico I think?
 
wseibert said:
I bought the Champion CJ8 at an auto parts store and it cost $3. When I went to exchange it for the right one, they didn't have the Champion and sold me the NGK for $0.79 more. Glad I didn't go to a Stihl dealer!

As for the spark plug chart posted by Woodslasher, the CJ8 plug that was in my saw when I bought it looked most like the first one labeled 'hot and lean', having a whiteish residue on it. Though I don't see much difference between that one and the one above and to the right labeled 'good'.

Thank you for all the replies. I'm learning that the whitish residue on the spark plug is related to fuel mix only, and not to the fact that the chain, bar and clutch drum were burnt up thorough lack of bar oil, overuse with a dull chain, or both.

Will
Click to expand...

The letter Y in the RCJ6Y designation is an extended tip type, totally different tip & a cooler plug. That’s likely why the CJ8 center was white hot.

Aspirin takers on here worry too much about plug manufacturers, but heat range is important. 🤣
 
hotshot said:
The letter Y in the RCJ6Y designation is an extended tip type, totally different tip & a cooler plug. That’s likely why the CJ8 center was white hot.

Aspirin takers on here worry too much about plug manufacturers, but heat range is important. 🤣
Click to expand...
The CJ8 is a non projected, non resister plug that's hotter in heat range than a RCJ6Y.
A hotter plug will not cause the spark plug to run whiteneither. That's a fuel to air mixture issue. Check the carb tuning is not set too line. If it's not check for air leaks.
 
bwalker said:
That old chart is for 4 cycles. Two stroke plugs don't often look like that and reading a used plug is if zero value in most cases.
Click to expand...
So reading used plugs in two strokes is not useful? I'm new to two strokes and so this is news to me. Thanks.
 

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